This invention relates to grease seals for frictionless bearings, a term used generally to include ball bearings, roller bearings, needle bearings and the like. More particularly this invention relates to molded seals for use in such bearings, having dispersed and embedded stiffening particles within the seal body.
It is known that the useful life and satisfactory operation of frictionless bearings are largely dependent on efficient lubrication and safe protection against access of foreign bodies or moisture between the working surfaces.
It is known to provide seals for frictionless bearings for the purposes of retaining grease and excluding contaminants, which seals are fabricated from metal disks. Such seals are reasonable effective, and have the advantage that expansion due to heat does not present a problem because the disk metal has essentially the same rate of expansion as the ring metal. A disadvantage of metal seals is the cost of assembly in that the seals are fitted into the ring grooves by a stamping or rolling operation wherein the flange of the seal is formed into the retainer seal groove, usually in the outer ring, whereby the seal is retained in the bearing. Another disadvantage of the use of metal disk seals is that these metal disks are relatively thick and rigid, and if the metal disk and the outer ring groove are not perfectly concentric, the forcing of the disk into the groove may produce an out-of-round condition in the outer ring resulting in binding of the assembled bearing.
Another known form of bearing seal is a conglomerate structure wherein a seal body of molded rubber or the like is molded around a metal stiffener such as a metal washer. This assembly provides a relatively rigid body to hold the seal in place within the groove of the outer ring, for example, and the outer periphery of the seal is sufficiently resilient to allow the seal to be snapped into the groove and to hold the seal within the bearing. The resiliency of the rubber will also accommodate expansion of the seal relative to the outer race. The fabrication of rubber rings with metal inserts is obviously expensive. An alternative configuration is to bond a metal stiffener such as a washer to a molded rubber seal, and this is also expensive since it requires a separate bonding operation.
From the standpoint of economic manufacture, it is desirable to produce a seal which can be fabricated from a moldable material such as a rubberlike material, provided that such a seal can be fabricated to have the desired characteristics, one being that the support body portion of the seal would have sufficient rigidity to enable the seal to retain itself within the groove of one bearing ring, and another being that the seal provides a flexible sealing lip or flange for sealing engagement with the other bearing ring.
It is known to provide seals made of an injection moldable material having particles embedded in a portion thereof to make a support portion, for example, more rigid than a sealing lip portion; and examples of such seals in a shaft seal configuration are disclosed in Hosford U.S. Pat. No. 2,538,198 and Rabe U.S. Pat. No. 3,957,278. The fabrication processes disclosed in both of these patents includes some special steps in addition to simple injection molding which increases the cost of bearing seals of this type.
A principal object of this invention is to provide an improved inexpensive and easily constructed bearing seal for retaining lubricant within a bearing and for excluding dirt therefrom.
Another object of this invention is to provide an improved bearing seal fabricated from a moldable material having dispersed and embedded particles for improving the stiffness of the seal body and enable that body to retain itself in sealing relation in the bearing assembly.
A further object of this invention is to provide an improved bearing seal fabricated from a moldable material having dispersed and embedded particles to reduce the expansion of the seal body resulting from heat buildup.
Still another object of this invention is to provide an improved bearing seal of a moldable material, having a rigid body to enable retention of the seal within one race of a bearing assembly, and having a flexible sealing flange for effective sealing relation with the other race of the bearing assembly.
Another object of this invention is to provide an improved bearing seal which is capable of economic fabrication, and which provides for economic assembly of the bearing seal in a bearing assembly.
These objects are accomplished in a seal ring for a frictionless bearing which is fabricated from an injection moldable material. The seal ring has an axially thick body, means on that body configured to be received in an annular seal groove of one of the bearing rings, and an axially thin peripheral sealing lip on the body for sealing engagement with the sealing surface of the other bearing ring. The moldable material has a plurality of dispersed particles which have a minimum transferse dimension greater than the axial thickness of the sealing lip. The body of the cured ring includes embedded filler particles to stiffen the body, and the sealing lip contains no such particles and is therefore more flexible. The objects are also accomplished in that seal ring in a bearing assembly which includes inner and outer rings, and a plurality of rolling bearings disposed between confronting faces of the ring. One of those confronting faces has a groove around at least one end thereof facing the other ring, to receive and retain the seal ring; and the other bearing ring has a seal surface confronting the groove to be engaged by the sealing lip of the seal ring. These objects are also accomplished in a method for fabricating a bearing seal for a frictionless bearing having a relatively rigid support body and a relatively flexible sealing lip. The method includes the steps: (1) designing said seal ring to have a relatively thick body and a relatively thin sealing lip the lip having a maximum selected thickness, and designing a mold for the seal ring; (2) forming the seal ring from an injection moldable material containing dispersed stiffening particles having a specified minimum transverse dimension which is significantly greater than the thickness of the sealing lip; and (3) effecting the setting of the moldable material to produce a molded body having embedded stiffening particles and an integral sealing lip free of said embedded stiffening particles.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawing.